1.6 genetic info Flashcards by jacob john

advantages of mitosis?

repair tissues,
replace dead cells/worn out,
growth,
asexual reproduction,
increase numbers quickly to take advantage of change in environment

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at what point in the cell cycle does DNA levels change?

double during synthesis/interphase

half during cytokinesis

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define centromere?

where the chromatids join together

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define chromatids?

after DNA copies itself, a single thread becomes two identical threads

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define chromosome?

long sections of DNA made of proteins, only visible during cell division

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define cytokinesis in animal cells?

constriction of parent cell from outside inwards as cytoplasm splits

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define cytokinesis in plant cells?

new cell plate forms across cell equator, from centre outwards creating a new cell wall

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define diploid number?

total number of chromosomes (46)

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define gene?

section of a chromosome/DNA strand that codes for a specific polypeptide/protein and its function

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define haploid number?

half of the diploid number (23) an example is a gamete

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define meiosis?

a cellular division that results in the formation of 4 gametes with a haploid number of chromosomes and genetic variation

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define mitosis?

a cellular division that produces two daughter cells that are genetically identical to the parent cell

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how long does the cell cycle last?

24 hours

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how many chromosomes do humans have?

each cell contains 46 chromosomes and 23 pairs (homologous pairs of chromatids)

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what are the 5 differences between mitosis and meiosis?

CCHANGED

mitosis
c - chromosome number unchanged
c- crossing over doesn’t occur
h - no homologous pairs
an
g - genetically identical daughter cells
e
d - 1 division results in 2 daughter cells

meiosis
c - chromosome number is halved
c - crossing over occurs
h - homologous pairs of chromosomes
an
g - genetically different daughter cells
e
d - 2 divisions resulting in 4 daughter cells

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what are the 5 stages of the cell cycle?

G1 - growth
S - synthesis
G2 - growth and prep for mitosis
M - mitosis
C - cytokinesis

what are the disadvantages of mitosis?

lacks genetic variation, cells cannot adapt in a change of environment

what are the four stages of mitosis?

prophase
metaphase
anaphase
telophase

(PMAT)

what happens to the chromosome number during mitosis?

maintains diploid number
but changes from having one thread to two during interphase

what is a tumour? what does it do?

irregular mass of cells, that prevent the normal function of body organs

what is cancer a result of? what does it form?

uncontrolled mitosis, forms tumours

what is the formula for mitotic index?

no. of cells in prophase, metaphase, anaphase, telophase

divided by

total number of cells

what is the mitotic index?

the percentage of cells in mitosis

what occurs at meiosis anaphase I?

very rapid
spindle fibres contracts
the chromosomes in each homologous pair gets separated and are pulled to opposite poles of the cell
the random arrangement of the chromosomes meant that each pole had a random mixture of paternal/maternal chromosomes

CENTROMERE IS NOT SPLIT AND CHROMATIDS ARE NOT PULLED APART

what occurs at meiosis metaphase I?

- the homologous pairs of chromosomes arrange **randomly** on the cells equator of the mitotic spindle - the random distribution and independent assortment of chromosomes produces more genetic variation - still pairs at this stage

what occurs during meiosis anaphase II?

- spindle fibres contract and centromeres split -chromatids are pulled to opposite poles

what occurs during meiosis metaphase II?

chromosomes line up separately on the spindle fibres at the equator, attached by its centromere

what occurs during meiosis prophase I?

NORMAL: - DNA condenses forming chromosomes, making chromatids visible as it duplicated during interphase in animal cells: - centrioles move to opposite poles - mitotic spindle develops and extends across from pole to pole - 1 paternal chromosome and 1 maternal chromosome associated a homologous pairs through synapsis (this is a bivalent) CROSSING OVER: - each bivalent has four strands, 2 chromosomes each with 2 chromatids. - these chromatids wrap around each other at the chaismata and exchange genetic information. NORMAL: - nuclear membrane disintegrates and nucleolus dissapears

what occurs during meiosis prophase II?

animal cells - new spindle develops at right angle to the old spindle plant cells - old spindle remains

what occurs during meiosis telophase I?

- end of first meiotic division - chromosomes are on opposite poles of cell - nuclear envelope reforms around each group of now haploid cells -chromosomes remain duplicated/condensed

what occurs during meiosis telophase II?

when reached poles, chromatids lengthen and become indistinct -spindle disappears -nuclear membrane reforms - cytokinesis occurs at the very end of telophase II

what occurs during mitosis anaphase?

very fast centromere splits spindle fibres contract chromatids separates to opposite poles

what occurs during mitosis metaphase?

chromosomes (two sister identical chromatids) arrange at equator of spindle chromosomes attach to the spindle fibres at the centromere contraction of spindle fibres draws individual chromatids apart

what occurs during mitosis prophase?

DNA condenses and forms chromosomes chromatids become visible animal cells - centrioles move to opposite poles of cell, mitotic spindle extends from centriole nuclear membrane disintegrates chromosomes are free in cytoplasm

what occurs during mitosis telophase?

final stage chromatids at poles are now chromosomes as they have gone back to one chromatid will full set of genetic info chromosomes uncoil and lengthen nucleus reforms and spindle breaks down

what occurs in interphase?

R: replication of DNA, replication of organelles with own DNA I: increase in cell size M: making new organelles S: synthesis of ATP, proteins, ribosomal material

what percentage of the cell cycle is interphase?

0.8

where do cancers come from?

a mutation in the gene that controls cell division

where does meiosis take place?

the reproductive organs of both plant and animal cells